I. Field of the Invention
The present invention relates to a method and apparatus for maximizing the energy efficiency in the operation of conventional central air-conditioning and heat pump systems. More specifically, the present invention relates to conventional central air-conditioning and heat pump systems having a ductwork system, a condenser fan motor, a compressor motor, and a blower motor wherein energy efficiency is achieved by electronically sequencing the above-referenced motors for minimum starting energy consumption, limit reverse temperature gains, increased production output, added component protection, extended component life and increased user comfort.
II. Description of the Prior Art
Most conventional central air-conditioning and heat pump systems currently being manufactured and presently in use are designed to be controlled by a thermostat centrally located in the area of a building that it serves. This provides automatic stratified temperature control for a desired comfort setting. When the thermostat senses a temperature change in the conditioned area, it energizes an air-conditioning system that normally includes a condenser coil, a condenser fan, a condenser fan motor, a compressor, a compressor motor, an evaporator coil, a blower fan, and a blower motor all connected through a closed refrigerant circuit, and a ductwork system for supplying comfort air or conditioned air which is not normally inside the comfort area or space. When a conventional system is energized, all motors are turned on at the same time causing a large consumption of energy, an immediate reverse temperature gain into the conditioned area, followed by comfort air production. This is the current industry standard of operation today. During the cycle, there is a small amount of duct loss which increases as the comfort demand increases, so that the shortest cycle would satisfy the most efficient operation. When the thermostat is satisfied, all motors are normally turned off at the same time resulting in a large waste of cooling capacity left in the evaporator and production left or remaining in the ductwork system and wasted compressor energy use.
U.S. Pat. No. 3,415,071 discloses a problem which occurs during the start-up of an air-conditioning system where excessive pressure builds up, and the patent provides for an improvement for that single start-up problem by operating the condenser fan on high speed for a timed period at the beginning of each cycle. The system stills wastes a large amount of energy each cycle since all motors are still turned on and off at the same time.
U.S. Pat. No. 4,672,816 discloses another problem which exists during the start-up of an air-conditioning system, as first disclosed in U.S. Pat. No. 3,762,178; and the problem is described as a bad odor produced at the beginning of each new cycle. This patent provides an improvement for delaying the blower-on start-up. This would improve another single starting problem only, but the sytem wastes a large amount of energy each cycle as the condenser fan and the compressor motor are still turned on together, and all of the motors are still turned off at the same time.
U.S. Pat. No. 4,423,765 discloses a problem involving wasted cooling production at the end of the cooling cycle and provides an improvement by running the blower at the end of the cycle, but creates a serious new problem, first disclosed in U.S. Pat. No. 3,545,218, which relates to de-energizing the condensing unit for short periods of time during the cooling cycle when the system should be producing comfort or conditioned air. This causes non-cooling periods; a large consumption of energy to restart the hot condensing unit shortly after it was turned off; increased blower running time which increases duct loss and energy consumption; and all motors are still started at the same time thereby introducing further energy inefficiencies.
U.S. Pat. No. 4,094,166 includes the same disadvantages as those of the patents cited above, but attempts to correct the problems associated with the non-cooling periods wherein the condensing unit is de-energized for short periods of time by adding a temperature sensor switch that can override the timer of the short de-energized periods thereby shortening the timed de-energization periods and possibly causing a condition known as "short cycling", which is well-known to those skilled in the art, as well as still having all of the problems and energy inefficiencies normally resulting from starting all of the motors at the same time.
A 1988 White Rodgers product catalog, on pages 20 and 21, discloses two heat pump thermostats that list a feature they refer to as "Computed EMR.TM. Program (Energy Management Recovery)", which works in the cooling cycle only, thus providing a means to run the blower for 60 seconds after the cooling cycle. This would recover some of the cooling left in the evaporator and ductwork, but offers no recovery for heating at all, and all of the motors are still started at the same time with the resultant inefficiencies associated therewith.
The above-references all have precise limited merits and some advantages for air-conditioning systems, but none of them achieves the energy efficiency, added protection, extended equipment life, and increased occupant comfort, as does that of the present invention.